This invention relates to the manufacture of magnetic laminations for inductive components and especially to a method and apparatus for continuously making, without a separate punching step, a strip of shaped amorphous metal laminations for electric machines and transformers and other inductive components.
Motors and transformers are made up of laminations with varying degrees of geometrical complexity, and conventional practice is that expensive carbide dies are used to punch laminations from steel strip. This process is time consuming and results in about 50% scrap which is sold back to the steel mill at scrap prices, and there are handling and transportation costs.
Amorphous metals are also known as metallic glasses and exist in many different compositions including a variety of magnetic alloys which include iron group elements and boron. Metallic glasses are formed from metal alloys that can be quenched without crystallization, and these solids have unusual and in some cases outstanding physical properties. Because their atoms are bound together by long-range metallic bonding, these alloys are malleable and good electrical conductors. Amorphous metals are mechanically stiff, strong and ductile, and the ferromagnetic types have very low coercive forces and high permeabilities. In electronic applications, these materials are capable of approximately equalling or in some respects exceeding the properties of conventional Fe-Ni, Fe-Co, and Fe-Si alloys, and offer a substantial cost saving. In power applications the potential improvement in properties is far greater; Fe.sub.80 B.sub.20 amorphous metal ribbons have one-fourth the losses, at a given induction for sinusoidal flux, of the best oriented Fe-Si sheet steel. Additional information is given in the article "Potential of Amorphous Metals for Application in Magnetic Devices" by F. E. Luborsky, J. J. Becker, P. G. Frischmann, and L. A. Johnson Journal of Applied Physics, Vol. 49, No. 3, Part II, March 1978, pp. 1769-1774.
Amorphous metal is manufactured in ribbons of 2 mil thickness or less; the thickness limitation is set by the rate of heat transfer through the already solidified material, which must be rapid enough that the last increment of material to solidify still avoids crystallization. This is several times smaller than currently used materials, but thinness gives amorphous metals an inherent advantage with respect to the geometrical control of eddy current losses. While it may be possible to construct inductive components from strips of uniform width, most electric machines and transformers are built with stacks of punched or shaped laminations. Laminations are designed to direct the magnetic flux toward the direction of action without air gaps between laminations, and therefore there are advantages in this type of magnetic structure. It would be easier to make the shaped lamination while processing the material than in punching the material after fabrication. This is particularly advantageous because of the additional punching necessary while using 2 mil thick strip.